The invention relates to an electron beam generator, particularly for an electron gun comprising a hot cathode and a control cathode which is disposed at a high-voltage insulator and can be connected to a high-voltage generator by means of a single-pole high-voltage cable. On top of the high-voltage insulator, there is disposed an insulating transformer for converting the cathode heating current. The primary winding of this transformer is connected to ground potential.
An electron beam generator of this kind for an electron gun for heating materials, particularly for welding, is known from DE-OS 33 686, to which U.S. Pat. No. 4,574,178 corresponds. Since the beam head is combined with a complete auxiliary voltage transmission by construction, a multi-pole cable with corresponding plug connections is no longer required for this known electron gun. Particularly the ohmic line losses which are caused by the heating current are reduced to almost zero. Since these losses are eliminated, the power to be transmitted is significantly reduced and the volume of the insulating transformers is no longer determined by the power to be transmitted but only by the necessary insulating distances. The power supply of the insulating transformers is at ground potential, and the control voltages are supplied via multiple plugs on the low-voltage potential of the beam head. Due to the much better capacitive coupling between the individual potentials, failures of components of the auxiliary voltage generator caused by arcovers and excess voltages connected therewith are already substantially reduced in the known electron gun. Bur there is still need to increase the operational reliability of the remaining electronic equipment od such electron beam apparatus.